Reconstructing infant diet and weaning behavior of ancient Maya from Lamanai, Belize using laser ablation -inductively coupled plasma -mass spectrometry (LA-ICP-MS)
This investigation represents the first extensive application of Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry to ancient dental analysis and paleodietary reconstruction. Enamel strontium composition is examined because it is a reliable hard tissue indicator of diet during enamel formation in childhood.
Here, infant diet and weaning behavior of pre-contact and colonial period Maya from Lamanai, Belize are reconstructed. Weaning is a critical dietary transition that has adaptive significance for later life. Since the strontium-calcium (Sr/Ca) ratio of solid food is high compared to that of breast milk, strontium composition of hard tissues developing before, and after, food supplementation can infer the timing of food introduction and weaning. Known timing of permanent enamel development allows correlation of canine enamel Sr/Ca values with age in childhood, which is facilitated by continuous laser microsampling.
The results indicate that enamel Sr/Ca faithfully records a biogenic signal associated with childhood dietary intake. The total Sr/Ca pattern generally follows the projected model of strontium change, with food supplementation starting at around nine months of age, which increases gradually until there is a substantial surge in food intake at approximately two years of age. Lamanai children continue to nurse afterward, possibly up to five years of age, but it comprises a minor nutritional component.
Significantly, the disadvantaged colonial Maya cohort has a reduced Sr/Ca pattern compared to elite Postclassic Maya, suggesting that colonial children may have exclusively breastfed for longer, delaying the age of food supplementation and weaning. Colonial Maya also exhibit greater Sr/Ca variation, reflecting dietary shifts that can be attributed to poorer nutrition and health. Female economic responsibilities partially account for the differences in colonial childcare practices. Additionally, enamel variation may reflect the different childhood origins (and weaning patterns) of possible migrants at Lamanai. Ultimately, the nature of infant diet and enamel Sr/Ca can be linked to interrelated ecological, political and economic factors.
LA-ICP-MS analysis reveals enamel Sr/Ca to be a sensitive gauge of the prolonged and complex process of weaning and it proves to be an ideal method of capturing the richness of early life history documented in sequentially-formed enamel.